A user was recently looking to get an earlier version of ST-Sim. When in SyncroSim if you select “File | Packages…” then “Install…” the default behavior is to get the most recent version of the package available on the SyncroSim package server. If you would like an earlier version of ST-Sim you can find it here:
https://github.com/ApexRMS/stsim/releases
You can download the ssimpkg file for the version you want and then select “File | Packages…” then “Install from File…” to navigate to the file you just downloaded. Note that you should be careful that the earlier version of ST-Sim that you are downloading is compatible with the version of SyncroSim that you currently have. You can also get earlier versions of SyncroSim here: https://syncrosim.com/downld-prev-versions/